You know why I find this so cool? If it weren’t for aura then this should have broken her wrist. Even if she were blocking with her forearm it’d be impressive. I saw something similar to this in real life where a guy tried to block a kick to the head with his forearm and the sheer force of the kick broke the guys bones. And Pyrrha here is blocking with her wrist. A joint bone. Joint bones are a lot easier to break than other bones in the body.
Unless Mercury can’t kick worth shit (which he probably can cause that’s his fighting style) then Pyrrha should have been in some serious pain (again, if it weren’t for aura). There’s also the part about how Mercury is kicking with a chunk of metal around his legs (even if it wasn’t metal it would still increase the force of the hit).
To sum it all up, Pyrrha is a badass.